ignorant question about UK system, if you please

[muriel_volestrangler]

1. If 100% of the coalition MPs voted for it, it would get through its Commons stages

since just a majority of votes cast in a division is needed. The House of Lords would need to pass it too; currently, the make-up of that is:

Conservative 28%
Labour 31%
Lib Dem 12%
Crossbench 23% (ie no party affiliation at all)
Bishops 3% (yes, we're still a partial theocracy)
Other parties 4%

So the coalition does not have enough votes to force something through the Lords. A constitutional measure such as this could be blocked by the Lords until a new general election. If the coalition got back into power then, it would have a mandate to enforce this, and the Lords would have to give way. Or they'd need support from crossbenchers or Labour peers in the Lords (or for some of them to abstain, anyway). Finally, the monarch in theory has the option to refuse to sign legislation that Parliament has passed. I think it's about 300 years since they've done that, though.